Our laboratory is specifically concerned with (1) interaction of phage T3 RNA polymerase with T3 DNA during specific transcription of phage DNA to synthesize late mRNAs; and (2) identification of eukaryotic initiation factors required for formation of functional 80S polypeptide chain initiation complexes and studies on the interaction of these protein factors with ribosomes, Met-tRNAf, GTP and mRNA during initiation complex formation. 1. Given the availability of modern techniques for restriction enzyme analysis, purification of defined DNA fragments, nucleic acid sequencing, and cloning, it will be possible to examine initiation and termination of transcription by T3 RNA polymerase in the following ways: (1) Since promoters and terminators for the T3 RNA polymerase have been precisely mapped on the T3 genome, it is now possible to obtain detailed DNA and RNA sequences of these promoters and terminators. The DNA sequence information of one such promoter has already been obtained in this laboratory. Similar studies of a number of other promoter regions of T3 DNA are now being carried out in order to identify a common (consensus) sequence that is necessary and sufficient for transcription by T3 RNA polymerase. (2) Studies will be undertaken to determine the role of various portions of promoter sequences in interaction with T3 RNA polymerase. 2. Three eukaryotic initiation factors, eIF-2, eIF-5 and eIF-6 (new one) have so far been identified and purified to homogeneity from calf liver extracts that are required for AUG-directed functional 80S initiation complex formation. Detailed studies on the interaction of each of these factors with ribosomes, Met-tRNAf, GTP, and mRNA during initiation complex formation are now being carried out.